This invention relates to cooling systems of internal combustion engines and more particularly to the radiator caps fitted to the coolant radiators of such engines.
The engines of modern automobiles generally use high pressure cooling systems requiring effective sealing of the radiator cap to prevent loss of coolant during normal operation of the engine. The radiator caps are normally fitted with spring-loaded washer-type seals which bear down on a ledge surrounding the bottom opening of the radiator filler neck so that when the cap is fitted to the filler neck the loading spring serves to hold the cap firmly in position and to provide the loading force for a spring-loaded seal around the filler opening. During normal operation of the engine this seal is sufficient to prevent escape of coolant but if for any reason the pressure within the radiator becomes excessively hot coolant is "blown" through the seal to escape through an overflow of venting duct through the side of the filler neck.
There is also an increasing use of coolant recovery systems in which coolant blown through the venting duct is collected in a bottle or other receptacle containing a reserve of liquid coolant and when the radiator cools coolant is drawn back into the radiator through the vent duct and the filler neck. This requires the radiator cap to be fitted with a suction operated valve within the main washer type valve seal, the suction operated valve being normally closed under the influence of a spring and/or pressure in the radiator but opening when the radiator pressure falls a determined amount below atmospheric pressure to permit reverse flow of coolant. The connection of the radiator cap to the upper part of the filler neck must also be adequately sealed to prevent loss of vacuum by ingress of atmospheric air. At present this additional sealing is achieved by fitting the radiator cap with a flat annular sealing element which bears down on the upper rim of the filler neck. It has been found however that such flat annular sealing elements do not always provide an adequate seal. Moreover, when the cap is rotated for release both the lower and upper seals are immediately broken and coolant may then be sprayed out under radiator pressure even in cases where safety stops are fitted to enable the cap to be rotated initially to a partially opened or venting position before it is removed. The present invention provides a radiator cap fitted with a novel type of sealing means which greatly alleviates these problems.